It is known that, in order to provide protection against bullets fired from a gun (with the speed in the range of 400 m/s), elements are commonly used, which are obtained by superimposing soft or flexible textile structures, composed of high resistance fibers. These structures can be impregnated with synthetic matrices to improve their ballistic behavior, that is to increase their capacity to absorb the impact, without altering their softness and flexibility. However, the so obtained ballistic structures are not suitable for stopping the incident bullet, and consequently to provide appropriate protection, in case of bullets fired from a rifle. In such cases, composite rigid structures are used.
Examples of rigid structures for ballistic protection are provided in U.S. Pat. No. 4,836,084, U.S. Pat. No. 4,613,535 and U.S. Pat. No. 6,893,704.
There are available on the market ballistic plates obtained by superimposing and compacting the layers of unidirectional fabrics, including UHMW polythene fibers, as for example, the fibers marketed with trademarks Dyneema® and Spectra®. Such structures would be able to stop bullets of the Nato 7.62 Ball type fired with a speed of 830 m/s, theoretically even with weight of about 16 kg/m2; however, they would not satisfy the requirements imposed by the regulations (in particular, the N.I.J. regulations 0101.03 and 0101.04), because the maximum trauma value allowed is 44 mm. Thus, it is necessary to use such plates in combination with a soft bullet-proof jacket that contributes to trauma reduction or to increase its weight up to about 19 kg/m2; such changes however, not only limit the practicability of the protective element, due to the higher weight, but they also cause the increase of its cost.